junits15
Well-Known Member
On a modern day performance car that is not used in any track or time trial events and the engine is not sustained at long (or very short/quick) intervals at very high speed/rpm - there is absolutely NO benefit to removing the catalytic converters.
Modern day catalytic converters (last 10 years) are very high flow and are not as restrictive as older systems of the past. Think about the performance cars out on the market now pushing 400-500-600HP right out of the box that were designed and built with catalytic converters in place.
You also cannot just remove the cats on an S550. Well... let's rephrase that - anyone can physically remove their cats...but error codes will surface AND even if bypassing the errors via known tricks, the car won't be running efficiently as designed (fact).
Operationally, you may need an aftermarket tune or a way to bypass the O2's, otherwise the engine will not perform at its optimum as designed and again multiple error codes may pop up.
---
Removing cats and or the resonator will greatly increase the sound (loudness) of the vehicle. Essentially you're removing inline "baffles" which are keeping the exhaust tone down. Once those baffles are removed, the car exhaust note will get much louder and you may notice increased drone as well at certain RPM ranges.
---
Does removing the cats improve exhaust flow? Yes BUT only to a degree as noted above regarding track use vs. daily driving. Adding LTH's and removing cats on a street driven vehicle where vehicle speed and RPM is not maintained, is erratic or sporadic stop/go intervals due to traffic, signal signs, signal lights, and lower speed limits in populated areas - it has NO benefit at all - other than the "loud factor".
If the car is to be used 90% or more for track use (drag racing, road racing or auto-X) and where rpm/speed is maintained higher than "normal" (ie: grocery getting), then deletion of cats and running LTH's can be beneficial where performance gains are not only recorded BUT also recognized in data.
In any instance a tune would also usually accompany such changes for track cars
where every bit of HP and closing time gaps is a need for gains.
If the car is aftermarket forced induction via turbos or supercharger, a tune is mandatory and again, removal of cats will only be beneficial to how the car is being used. If it's just putzing around town @45 mph for a run to a store and back, there's just no benefit.
If you're in a State or region that requires emissions inspections - removal of cats is not only going to be a PIA come inspection time - but if caught running without, that can be a pricey monetary fine.
Removal of cats will in some instances also increase exhaust smell (raw fuel smell) and the excessive loudness can bring attention to you.
No one can tell you what to do - it's your vehicle. Just take note of the above, especially if you're in a region where annual emissions inspections are a requirement.
Absolutely beautiful response, I have been advocating people leave their cats in for years.
To date I’ve never seen any real world before/after data proving that the catalyst itself offers any appreciable restriction.
Sponsored
